The present invention relates to heating apparatus and heating method for supply of gaseous fluid, and more particularly, to such apparatus and method in which a relatively low temperature gaseous fluid is heated to a high temperature and a heated supply flow at a high temperature is fed to an equipment, such as a combustion furnace or a combustion equipment to be supplied with high temperature gaseous fluid.
A variety of combustion furnaces or combustion equipments, such as waste incinerator, waste gasification melting furnace, boiler, waste heat recovery boiler, heating furnace, and coal gasification furnace, are practically used in any kind of facilities, e.g., public facility, power generation plant, chemical plant or the like. In general, such a combustion furnace or combustion equipment is provided with a gaseous fluid feeding device for feeding combustion air to a combustion area of the furnace, and the feeding device includes heating means, such as a heat exchanger utilizing the waste heat of the combustion exhaust gas, preheating apparatus or pre-combustor for preheating or causing pre-combustion of combustion air. The heating means heats or preheats intake air or combustion air and feed a high temperature air flow or preheated air flow to a combustion means or firing means such as a burner.
FIG. 34 is a schematic flow diagram generally illustrating an arrangement of a waste gasfication melting furnace provided with such heating means.
A furnace 6 constituting a waste gasfication melting furnace is connected to an intake system with a forced draft fan 102 and a heating device 101, and an exhaust system 7 including a cooling device 71, a flue gas treatment system 72 and a stack 73. The system 7 is, in general, equipped with a series of exhaust gas treatment means, such as a dust collector and a exhaust gas denitration device. In the furnace 6, a melting furnace region 60 with a molten waste fluidized zone 61 in its bottom part, and an upper secondary combustion region 62 above the region 60.
The furnace 6 has a waste inlet opening 63 for charging waste into the region 60 and a secondary material inlet opening 64 for supplying supplementary materials and fuel thereto, the opening 63 being connected to conveying means 66 through a shute 65 and a feeder (not shown) and the opening 64 being connected to a supplementary material feeder (not shown) by a conveyor 67.
In the region 60, a plurality of burner throats 50, 51, 52 are provided below the openings 63 and the conveyor 67. The primary throat 50 in the zone 61 is joined to a heating device 101 through the preheated air supply line HA. Pre-combustion or primary combustion of intake air induced through an inlet 103 and the fan 102 is carried out in the device 101, which feeds high temperature preheated combustion air to the throat 50 through the line HA.
Combustion apparatus provided with such kinds of air heating apparatus permits the oxygen density or excess air ratio of the preheated air to decrease, owing to the pre-combustion or primary combustion. In order to compensate for the reduction of the oxygen density and to ensure a desired combustion reaction in the furnace, the heating device 101 is provided with an oxygen supply line 104 joined to the line HA. The line 104 is connected to an oxygen source 105 having oxygen cylinders, which adds a predetermined flow rate of oxygen (O2) to the preheated air flow through the line HA.
Provision of an oxygen feeder, however, results in an increase of initial construction costs for the furnace or combustion equipment, as well as complication of maintenance of the system. Further, such an expensive oxygen cylinder or the like has to be periodically supplied to the oxygen feeder. Thus, since routine maintenance is necessitated for the oxygen feeder, costs for running and maintaining the system is increased. This is undesirable for practical use in long years.
Research and development as regards a variety of coal firing apparatus, Such as coal fired power generation boiler, pulverized coal firing boiler and coal gasification system, and various types of coal fired combined cycle power generation systems, such as AFBC, PFBC or pressurized CPC, are widely conducted in recent years in response to political or social requirements. In general, these kinds of coal fired systems or equipments are provided with heating devices, such as a heat exchanger using waste heat of combustion exhaust gas, which heat or preheat combustion air of ambient atmosphere to an appropriate temperature and feed the preheated air to combustion means such as a burner for pulverized coal.
Various types of coal fired devices are known, e.g., stoker combustion type, pulverized coal fired type, fluidized bed type and so forth. In general, the pulverized coal fired type of boiler is preferably adopted as a coal fired boiler in with a large capacity, such as a boiler of power generation station, since such type of boiler presents relatively good response and controllability as to variation of load and effects a desirable combustion efficiency.
In such a pulverized coal fired boiler, coal particles are carried with primary air into a combustion area and rapidly heated by a burner for pulverized coal. As combustion exhaust gas of the boiler contains a relatively large amount of fuel NOx, thermal NOx, sulfur and smoke dust (dust, fly ash), an exhaust system is generally equipped with a series of desulfurizer, denitration device, and electrostatic precipitator (ESP) and so forth.
FIG. 35 is a schematic flow diagram illustrating such a coal fired system.
A coal fired power generation boiler plant comprises a burner for pulverized coal 120 and a pulverized coal fired boiler 110, and the burner 120 is connected with a pulverized coal feeding line CS and a secondary air feeding line CA. The line CA is connected to a forced draft fan 121 through a heating section 181 of a rotary air-preheater APH for heating the secondary air to an order of 300xc2x0 C. The fan 121 feeds intake air from an air intake port 122 and an air intake line OA to the preheater APH and the air preheated thereby is fed to the burner 120 through the line CA. The pulverized coal and air mixed in the burner 120 fires in a combustion area 150 of the boiler 110 to heat superheater 151, reheater 152 and economizer 153 in the area 150, and combustion gas is exhausted through an exhaust gas line E11. The exhaust system including lines E11 to E20 is equipped with exhaust treatment devices wherein electrostatic precipitator (ESP) 171, ammonia injector 172 connected to an ammonia source (not shown), selective catalytic reduction device 173 with catalyst units, heat accumulating section 174 of a rotary air preheater APH for heat recovery, forced induce fan 175, heat accumulating section 176 of a gas-gas heater GGH, booster fan 177, desulfurizer 178, heat emission section 179 of the gas-gas heater GGH, and stack 180 arranged in series.
A high-cycle regenerative combustion system which is capable of preheating such a supply flow of air to the combustion equipment is disclosed in Japanese patent application No. 5-6911 (Japanese patent laid-open publication No. 6-213585) of the present applicant. This system developed by the present applicant includes a regenerator of honeycomb structure with a number of narrow channels or fluid passages which exhibits a high temperature effectiveness and a high volumetric efficiency. High temperature combustion exhaust gas and low temperature supply fluid flow alternately passes through the regenerator, so that the supply flow is heated to a high temperature above 800xc2x0 C. by heat exchange with the exhaust gas through the regenerator.
However, in this kind of system, high temperature combustion exhaust gas effluent immediately after a combustion step has to be introduced into the regenerator, since the high temperature gas possessing sensible heat enough to be efficiently transferable to the low temperature supply flow. Therefore, it would be difficult to apply the conventional regenerative heat exchange system to the aforementioned waste gasification melting furnace or the like, in which the high temperature exhaust gas cannot be readily used.
Further, the fluid passages of the honeycomb regenerator of the above regenerative system is apt to be relatively easily blocked by dust, smoke dust, ash, fly ash or the like, and therefore, relatively clean combustion exhaust gas at a high temperature, which does not contain dust or other foreign matters, should be introduced into the honeycomb regenerator. Therefore, it would be difficult to effectively use such a regenerator in a combustion system which may produce combustion exhaust gas containing dust, ash or other foreign matters.
For instance, high temperature exhaust gas of coal fired combustion equipment includes a substantial quantity of smoke dust, and therefore, the narrow channels of the regenerator are apt to be blocked in a relatively early stage. Therefore, it would be difficult to apply the aforementioned regenerative system to an exhaust system of a coal fired equipment. Thus, it is necessary to develop a heat exchange system applicable to such kinds of combustion equipments.
It is therefore an object of the present invention to provide a heating apparatus and a heating method for heating supply of gaseous fluid which heats a relatively low temperature gaseous fluid and feeds a heated supply flow to a high temperature gaseous fluid introduction equipment, wherein the supply flow can be heated to a high temperature without substantially changing the property of the supply flow, such as its oxygen density.
Another object of the present invention is to provide such an apparatus and method which enable the supply of gaseous fluid for combustion to be heated to a high temperature range above 800xc2x0 C., preferably, above 1,000xc2x0 C.
Still another object of the present invention is to provide such apparatus and method which is capable of producing water gas and which can continuously feed a water gas flow to an equipment consuming the water gas, such as a coal gasification system or a gas turbine plant.
To this end, the present invention provides a heating apparatus for supply of gaseous fluid which heats a relatively low temperature gaseous fluid and feeds a heated supply flow to a high temperature gaseous fluid introduction equipment, which comprises a heat exchanger provided with a fluid passage through which the low temperature gaseous fluid flow passes and adapted to heat the low temperature gaseous fluid, a splitting area for dividing a heated supply flow of the gaseous fluid into first and second gaseous streams, the supply flow having a temperature raised as a result of its passing through said heat exchanger, and a combustion area into which combustible matter is introduced so that a combustion reaction of the combustible matter takes place therein. The heat exchanger, combustion area and splitting area are in communication with each other, so that the second stream is fed to the above equipment, and the hot gas produced by said combustion reaction in the combustion area is exhausted through the heat exchanger. The heat exchanger accumulates heat in its heat-transferable contact with the hot gas and emits the heat in its heat-transferable contact with said low temperature gaseous fluid.
According to the arrangement of the present invention, the hot gas produced in the combustion area passes through the fluid passage of the regenerative heat exchanger to heat it. The hot gas is cooled by the heat accumulating action of the heat exchanger in which the sensible heat of the hot gas is heat-transferred or transmitted to the regenerator and stored therein, whilst the low temperature fluid is heated to raise its temperature with the heat emitting action of the heat exchanger in which the sensible heat stored in the regenerator is transferred to the low temperature fluid to heat it. Thus, the heat exchange between the low temperature flow and the hot gas effected by means of the regenerator allows the low temperature flow to be heated or preheated to a high temperature.
The present invention also provides a heating method for heating supply of gaseous fluid in which a relatively low temperature gaseous fluid is heated and a heated supply flow is fed to a high temperature fluid introduction equipment, comprising first and second heating processes. The first heating process includes steps of introducing the low temperature gaseous fluid through a first heat exchanger at a high temperature so as to heat the low temperature gaseous fluid tip to a high temperature with a heat exchange action in its heat transferable contact with the first heat exchanger, splitting the heated supply flow into first and second gaseous streams, feeding the second stream to the equipment, generating a combustion reaction of the heated supply flow and/or the first stream in a combustion area, introducing hot gas produced by the combustion reaction into a second heat exchanger, and exhausting the hot gas therethrough so that sensible heat of the hot gas is accumulated in a regenerator of the second heat exchanger with a heat exchange action in a heat transferable contact between the hot gas and the second heat exchanger. The second heating process includes steps of introducing the low temperature gaseous fluid through the second heat exchanger at a high temperature so as to heat the low temperature gaseous fluid up to a high temperature with a heat exchange action in its heat transferable contact with the second heat exchanger, splitting the heated supply flow into the first and second gaseous streams, feeding the second stream to the equipment, generating a combustion reaction of the heated supply flow and/or the first stream in the combustion area, introducing hot gas produced by the combustion reaction into the first heat exchanger, and exhausting the hot gas therethrough so that sensible heat of the hot gas is accumulated in a regenerator of the first heat exchanger with a heat exchange action in a heat transferable contact between the hot gas and the first heat exchanger, The first and second heating processes are alternately changed over in a predetermined time interval so that the low temperature flow is continuously heated to the high temperature.
From another aspect of the present invention, this invention provides a heating system for heating a supply of gaseous fluid comprising a plurality of the above heating apparatus arranged in parallel.
From still another aspect of the present invention, a preheating apparatus for preheating combustion air for a combustion furnace, a deodorization apparatus for exhaust gas, a repowering apparatus for exhaust gas of a turbine, a water gas generator, or an inert gas heating apparatus are provided, each having the above described apparatus for heating the supply flow of gaseous fluid.
In a preferred embodiment of the present invention, the first stream is introduced into the combustion area, and the combustible matter generates the combustion reaction in the existence of the first stream and maintains the combustion. The low temperature fluid can be substantially heated to a high temperature range equal to or higher than 800xcx9c1,000xc2x0 C. by the substantially direct heat transmission of the regenerator, with the properties of the fluid, such as its initial oxygen density being kept.
In accordance with another preferred embodiment of the present invention, the heated supply flow is introduced into the combustion area, and the combustible matter generates and maintains the combustion reaction in the existence of the heated supply flow. Thus, the low temperature fluid can be heated to a high temperature range equal to or higher than 800xcx9c1,000xc2x0 C. by the substantially direct heat transmission through the regenerator and the heated flow can take the combustion reaction in the combustion area.
According to a preferred embodiment of the present invention, the apparatus may be provided with a fluid flow introduction passage for receiving the low temperature gaseous fluid flow, a combustion exhaust gas passage for exhausting the hot gas effluent, a heated supply flow delivery passage for delivering the second gaseous stream to the gaseous fluid introduction equipment, changeover means connected to the introduction passage and the combustion exhaust gas passage, first and second fluid flow passages connected to the changeover means, first and second heating devices connected to the first and second fluid flow passages, and the splitting area which is in communication with the first and second heating devices and in communication with delivery passage. The first heating device may have the first heat exchanger connected to the first fluid flow passage and the first combustion area arranged in series with the first heat exchanger, wherein the first fluid flow passage, the first heat exchanger and the first combustion area are in communication with each other so as to direct the heated supply flow to the splitting area. Similarly, the second heating device may have the second heat exchanger connected to the second fluid flow passage and the second combustion area arranged in series with the second heat exchanger, wherein the second fluid flow passage, the second heat exchanger and the second combustion area are in communication with each other so as to direct the heated supply flow to the splitting area. The splitting area is preferably provided with splitting means for splitting the heated supply flow into the first and second gaseous fluid streams and directing the first stream to the first or second combustion area. Further, each of the first and second combustion areas are preferably provided with combustion means for generating the combustion reaction of the combustible matter and maintaining the combustion reaction in a predetermined period of time.
In such a preferred embodiment, the combustion exhaust gas in the combustion area passes through the fluid passages of the regenerator of the first or second heat exchanger so as to heat the regenerator. Tile switching control with respect to the changeover means is conducted in a predetermined time interval, so that the heat accumulation action and the heat emission action are alternately repeated in a short term of time, whereby the sensible heat processed by the combustion exhaust gas in the combustion area is transferred and transmitted to the regenerator and accumulated therein during the heat accumulation action, and the sensible heat stored in the regenerator is dissipated to the low temperature fluid to be heated during the heat emission. As the result, the heat exchange action between the low temperature fluid and the combustion exhaust gas is successively carried out by the regenerator, so that the low temperature fluid can be heated to a high temperature equal to or higher than 800xcx9c1,000xc2x0 C. by the substantially direct heat exchange therebetween through the regenerator.
Preferably, the changeover means takes a first position in which the introduction passage is in communication with the first fluid flow passage and the combustion exhaust gas passage is in communication with the second fluid flow passage, and a second position in which the introduction passage is in communication with the second fluid flow passage and the combustion exhaust gas passage is in communication with the first fluid flow passage. The changeover means is adapted to be alternately switched to either of the first and second positions in a predetermined time interval. The combustion exhaust gas is delivered through the regenerator of the first heat exchanger to the first fluid flow passage, while the combustion means of the first combustion area is in a combustion operation in the second position of the changeover means. On the other hand, the combustion exhaust gas is delivered through the regenerator of the second heat exchanger to the second fluid flow passage while the combustion means of the second combustion area is in a combustion operation in the first position of the changeover means. More preferably, the changeover means is alternately switched to either of first and second positions in a predetermined time interval set to be no longer than 60 seconds, preferably no longer than 30 seconds, so that each of the regenerators of the first and second heat exchangers repeatedly perform heat accumulation and heat emission in correspondence with the time interval to heat the low temperature fluid and cool the combustion exhaust gas.
The splitting may divide the heated flow into the first and second streams by control of fluid pressure (control of static pressure and/or dynamic pressure). The splitting means defined by an orifice or restriction can effect a function to control fluid pressure balance of the heating devices and a function to control direction of the first and second streams. In a preferred embodiment, the splitting area is provided with a fluid passage inclined to the center axis of the heating device, and regulation and resistance means positioned in the inclined passage for regulating the direction of the flow and increasing pressure loss of fluid flow. This means may be a honeycomb structure which is substantially the same as the structure of the regenerator.
In a preferred embodiment, the heating apparatus comprises a fuel feed line for introducing a fuel into the combustion area and fuel control means for controlling the fuel feed line. The fuel may be combustible exhaust gas of a combustion furnace. The hydrocarbon fuel or the combustible exhaust gas is alternately introduced into the combustion areas to cause the combustion reaction therein.
The heating apparatus may be provided with first and second exhaust gas introduction passages for introducing combustion exhaust gas, which is produced in a combustion furnace or combustion equipment, into the combustion area, and control valve means for controlling the flow of the introduction passages.
Preferably, the first and second heating devices are arranged in parallel and in communication with each other through a communication passage defining said splitting area. The communication passage is provided with a constriction functioning as an orifice regulating a fluid pressure of said heated supply flow and act as a deflector directing the fluid in an inlet opening of the heated supply flow passage.
In one preferred embodiment of the invention, odorous exhaust gas of painting process or the like, in which odorous components or odorous matters are contained, is alternately introduced into the first and second combustion areas through odorous exhaust gas introduction means so as to take a thermal decomposition reaction therein for deodorizing the odorous gas.
In another preferred embodiment of the invention, the low temperature fluid essentially consists of ambient atmospheric air or inert gas, and the second stream heated to a high temperature of at least 800xc2x0 C., preferably a temperature equal to or higher than 1000xc2x0 C., is delivered to a combustion furnace or a combustion equipment as being a combustion air flow or an inert gas flow at a high temperature.
In still another preferred embodiment of the invention, exhaust gas of a turbine is alternately introduced into the first and second combustion areas and the second stream is directed to a waste heat recovery boiler defining the high temperature gaseous fluid introduction equipment.
According to a preferred embodiment of the invention, the regenerator is a ceramic honeycomb structure having a number of fluid passages or channels through which the low temperature fluid and the exhaust gas of the combustion area alternately pass. The regenerator may have channels defined by cell holes of a square or triangular cross-section, and the thickness and of the cell wall are pitch preferably corresponds to the dimensions ensuring the maximum value of the volumetric efficiency and the temperature effectiveness ranging from 0.7 to 1.0. More preferably, the thickness of the cell wall is no greater than 1.6 mm and the pitch thereof is no greater than 5.0 mm.
In a preferred embodiment of the invention, combustion assist air is additionally introduced into the combustion areas through assist air feeding means so as to supplement or compensate the combustion air required for the combustion reaction in the combustion area. The assist air promotes the combustion reaction so that substantially complete combustion can be achieved in the combustion area and the heat sufficient for the heat exchange with the low temperature fluid can be obtained.
In a preferable embodiment of the invention for production of water gas, the heating apparatus comprises a superheated steam introduction passage for feeding superheated steam as the low temperature gaseous fluid, an exhaust gas passage for exhausting the hot gas produced in the combustion area, changeover means connected to the introduction passage and the exhaust gas passages, first and second fluid flow passages connected to the changeover means, first and second heating devices connected to the first and second fluid flow passages, and a water gas delivery passage to be in communication with the first and second heating devices. The first heating device is provided with the first heat exchanger connected to the first fluid flow passage and the first combustion area arranged in series with the first heat exchanger, and the second heating device is provided with the second heat exchanger connected to the second fluid passage and the second combustion area arranged in series with the second heat exchanger. The first and second combustion areas are provided with combustion means for feeding oxidizer and hydrocarbon fuel to the superheated steam heated by heat exchanges. The first and second heat exchangers heat the superheated steam to a high temperature so that the water gas reaction of the high temperature steam takes place in the heat exchangers and the combustion areas. Tile water gas thus produced is split into the first and second stream in the splitting gas, and the second stream is fed to a water gas consuming device such as a coal gasification device or a power generation system. The first stream is directed into the other combustion area to take a combustion reaction in the existence of the oxidizer and fuel to produce a high temperature gas, which is discharged through the heat exchanger. Tile sensible heat of the gas is accumulated in the regenerator.
In a preferable embodiment of the invention for coal fired gasification process, a low temperature combustion air fed to a coal fired combustion device or a pulverized coal fired boiler is introduced into the heating apparatus, in which the combustion air is heated by the heat exchanger at a high temperature. The apparatus feeds a second stream at a high temperature to the coal fired device. Combustion exhaust gas of the coal combustion device containing combustible matters is introduced into the combustion area of the heating apparatus to be mixed with the first stream at a high temperature, so that a secondary combustion reaction of the exhaust gas is caused therein. The secondary combustion exhaust gas produced by the secondary combustion reaction is exhausted through the heat exchanger. Tile sensible heat of the secondary combustion exhaust gas is accumulated in the regenerator by heat exchange therewith. The first and second heating processes are alternately carried out in a predetermined time interval, so that the low temperature supply air is continuously heated to the high temperature range by heat exchange between the coal combustion exhaust gas and combustion air though the regenerator. Thus, the preheated air at a high temperature is introduced into the combustion device.
In a preferred embodiment of the present invention, the coal combustion device is a pulverized coal boiler and the combustible exhaust gas thereof contains unburnt fuel components, hydrogen and carbon. The preheated air is heated tip to a temperature above the self-ignition temperature of the combustible components and the combustion exhaust gas is alternately fed to the first and second combustion area to be mixed with the first stream therein, thereby taking a secondary combustion reaction.